In data processing systems, disc drives are often used as storage devices. Such drives use rigid discs, which are coated with a magnetizable medium for storage of digital information in a plurality of circular, concentric data tracks. The discs are mounted on a spindle motor, which causes the discs to spin and the surfaces of the discs to pass under respective hydrodynamic (e.g. air) bearing disc head sliders. The sliders carry transducers, which write information to and read information from the disc surfaces.
An actuator mechanism moves the sliders from track-to-track across the surfaces of the discs under control of electronic circuitry. The actuator mechanism includes a track accessing arm and a suspension for each slider assembly. The suspension includes a load beam and a gimbal. The load beam provides a load force that forces the slider toward the disc surface. The gimbal is positioned between the slider and the load beam, or is integrated in the load beam, to provide a resilient connection that allows the slider to pitch and roll while following the topography of the disc.
The slider includes a bearing surface, which faces the disc surface. As the disc rotates, the disc drags air under the slider and along the bearing surface in a direction approximately parallel to the tangential velocity of the disc. As the air passes beneath the bearing surface, air compression along the air flow path causes the air pressure between the disc and the bearing surface to increase, which creates a hydrodynamic lifting force that counteracts the load force and causes the slider to lift and fly above or in close proximity to the disc surface.
Gimbals which support the head slider must allow the slider to rotate in pitch and yaw so as to conform to the plane of the disc while minimizing the torque applied to the slider, in order for the slider to fly properly over the disc. Gimbals must also be stiff in plane, to minimize undesired sideways motion that causes positioning error, and resist damage from stiction events where a significant force is required to free the head from the disc at start up. In the normal direction of disc rotation the gimbal struts are in tension, so buckling is not an issue, but under certain conditions a significant reverse rotation of the disc can occur, which can cause the gimbal struts to buckle. The gimbal buckling can then force the load beam up, which increases the preload force, preventing the slider from breaking free of the stiction, so that the gimbal is severely deformed and the drive is destroyed. One way of increasing the gimbal strut resistance to buckling is to increase the thickness or width, or decrease the length, but these all increase the stiffness in the desired gimbaling modes as well, which degrades the normal operation of the gimbal.
Embodiments of the present invention address these and/or other problems, and offer advantages over the prior art.